LM3S9B81 Datasheet, PDF (811/1155 Pages) Texas Instruments – Stellaris® LM3S9B81 Microcontroller

Stellaris® LM3S9B81 Microcontroller
and the XTALNPHY pin should be left unconnected. See “Ethernet Controller ” on page 1100 for more
information regarding the specifications of the Ethernet Controller.
19.3.3.2
Auto-Negotiation
The Ethernet Controller supports the auto-negotiation functions of Clause 28 of the IEEE 802.3
standard for 10/100 Mbps operation over copper wiring. This function is controlled via register
settings. The auto-negotiation function is turned on by default, and the ANEGEN bit in the Ethernet
PHY Management Register 0 - Control (MR0) is set after reset. Software can disable the
auto-negotiation function by clearing the ANEGEN bit. The contents of the Ethernet PHY Management
Register - Auto-Negotiation Advertisement (MR4) are reflected to the Ethernet Controller’s link
partner during auto-negotiation via fast-link pulse coding.
Once auto-negotiation is complete, the SPEED bit in the Ethernet PHY Management Register 31
– PHY Special Control/Status (MR31) register reflects the actual speed. The AUTODONE bit in
MR31 is set to indicate that auto-negotiation is complete. Setting the RANEG bit in the MR0 register
also causes auto-negotiation to restart.
19.3.3.3
Polarity Correction
The Ethernet Controller is capable of automatic polarity reversal for 10BASE-T and auto-negotiation
functions. The XPOL bit in the Ethernet PHY Management Register 27 –Special Control/Status
(MR27) register is set to indicate the polarity has automatically been reversed.
19.3.3.4
MDI/MDI-X Configuration
The Ethernet Controller supports the MDI/MDI-X configuration as defined in IEEE 802.3-2002
specification through software assistance. The MDI/MDI-X configuration eliminates the need for
cross-over cables when connecting to another device, such as a hub. Software can implement the
MDI/MDI-X configuration using a function outlined by the pseudo code below. This code should be
called periodically using one of the available timer resources on the Stellaris^® microcontroller such
as the System Tick Timer or one of the General Purpose timers. The following code refers to the
LINK bit in the Ethernet PHY Management Register 1 - Status (MR1), the ENON bit in the Ethernet
PHY Management Register 17 - Mode Control/Status (MR17), and the EN bit of the Ethernet
PHY MDIX (MDIX) register.
//
// Entry Point for MDI/MDI-X configuration.
//
//
// Increment the Link Active and Energy Detect Timers using the elapsed time
// since the last call to this function. If using a periodic timer, the
// elapsed time should be a constant (the programmed period of the timer).
//
Increment Link Active Timer
Increment Energy Detect Timer
//
if(No Ethernet Link Active)
{
//
// If energy has been detected on the link, reset the Energy Detect Timer.
// If it is a "new" energy detect, reset the link detect timer also.
June 29, 2010
811
Texas Instruments-Advance Information